Flexible polyurethane foams are widely used in products such as mattresses and seating, where safety considerations require that they exhibit effective fire retardant properties. Flexible polyurethane foams may be made to possess satisfactory resistance to ignition and/or flame propagation by the addition of one or more flame retardant substances.
Melamine is a flame retardant commonly employed in the preparation of polyurethane foams. Melamine is generally dispersed in a suspending liquid before foaming for the ease of handling. Suitable suspending liquids exhibit low solvency for and are chemically inert to melamine. A common suspending liquid is high molecular weight liquid organic polyols.
U.S. Pat. No. 4,293,657 teaches the use of melamine dispersions in polyol wherein the melamine has a particle size of less than 10 μm and is produced by crushing in situ in the polyol at high localized energy densities. A dispersion stabilizer is also a necessary ingredient. In addition, it discloses that the polyols may be partially replaced by monofunctional primary and/or secondary hydroxyl group-compounds having molecular weights of 200 to 16,000.
U.S. Pat. No. 5,125,952 discloses a storage-stable concentrated liquid dispersion of melamine that contains fine melamine particles, admixed with a chemically inert suspending liquid and a chemically inert thickening agent. Effective thickening agents include xanthan gums, carrageenans, polyacrylamide, chemically treated cellulose, and clays.
U.S. Pat. No. 4,892,893 discloses the preparation of flame retardant flexible polyurethane foams incorporating substantially uncrushed melamine in an amount ranging from about 5 weight percent to about 25 weight percent of the weight of the foam.
The disclosure of the previously identified patents is hereby incorporated by reference.